Canada Grounds Flights at Toronto and Montreal as US Outage Ripples North

Two of Canada's biggest airports issued ground stops on Friday as the FAA's nationwide air traffic control outage pushed disruption across the border. NAV CANADA, the privately run nonprofit that owns and operates Canada's civil air traffic system, said its own systems are "operating normally" — the stops exist to "safely manage traffic volumes."

The numbers driving that decision are large. As of 6:20 pm Eastern time, more than 2,700 flights within, to, or out of the US had been canceled, with another 10,500 delayed, according to FlightAware.com. For context, that's roughly one in every three scheduled US flights on a typical Friday either scrubbed or running late.

What does this change for travelers and airlines?

NAV CANADA's public guidance was blunt. "Travellers should expect delays and check with their airline," it said on X. That's the practical takeaway for anyone flying into or through Canada tonight: the airspace system itself is healthy, but airport aprons and gates are about to get crowded.

The diversion math explains why. Cirium, an aviation analytics company, said at least 600 flights had been diverted so far on Friday, with airports including Denver, Chicago, Los Angeles, and Cleveland taking on additional aircraft. Canadian hubs — the ones now in ground stop — are the natural landing spots for US-bound international flights that can't reach American airspace.

Mark Stephens, a retired Delta Air Lines pilot, told Business Insider that the airports may be preparing for exactly that wave of US-bound international diversions. He added that planes already on the ground at the airports will return to their gates, meaning traffic management will be imperative to handle the potential increase in volume.

The mechanics of a ground stop

A ground stop sounds dramatic, but here it's a volume-control tool. NAV CANADA isn't reporting a system failure — it's pacing arrivals and departures so that diverted wide-bodies, returning gate traffic, and scheduled flights don't saturate apron space at Toronto and Montreal.

For airline operations teams, that means three things to watch:

• Gate availability at Toronto and Montreal as parked aircraft cycle back from runways.
• Crew and slot knock-on effects once the US ground stop lifts and diverted flights refile their routes.
• Cascading delays on transborder routes, since a diverted international flight doesn't simply rejoin the queue instantly.

The US side of the event remains the bigger story. The FAA's nationwide ground stop had already produced the 2,700 cancellations and 10,500 delays tallied by FlightAware by early Friday evening, and Business Insider reported no end in sight at the time. Microsoft and the vendor behind the FAA's SMART AI system have both said the ground stop wasn't their fault, according to separate Business Insider coverage.

Why Canada's move matters

Canada's airports are effectively becoming the pressure-release valve for North American traffic. Every US-bound flight that diverts north takes a gate, a fueling slot, and a crew's duty clock — resources that were planned around a normal Friday schedule.

With more than 600 diversions already logged by Cirium and the US outage unresolved, the practical question for Friday night and into the weekend is how fast Toronto and Montreal can cycle diverted aircraft back out. Until the FAA lifts its stop, NAV CANADA's ground stops are the traffic-management floor holding that system together.